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Subject[PATCH v2 1/3] clocksource: davinci: only enable tim34 in periodic mode once it's initialized
Date
From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

The DM365 platform has a strange quirk (only present when using ancient
u-boot - mainline u-boot v2013.01 and later works fine) where if we
enable the second half of the timer in periodic mode before we do its
initialization - the time won't start flowing and we can't boot.

When using more recent u-boot, we can enable the timer, then reinitialize
it and all works fine.

I've been unable to figure out why that is, but a workaround for this
is straightforward - don't enable the tim34 timer in periodic mode until
it's properly initialized.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/clocksource/timer-davinci.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/timer-davinci.c b/drivers/clocksource/timer-davinci.c
index 62745c962049..2801f21bb0e2 100644
--- a/drivers/clocksource/timer-davinci.c
+++ b/drivers/clocksource/timer-davinci.c
@@ -62,6 +62,7 @@ static struct {
struct clocksource dev;
void __iomem *base;
unsigned int tim_off;
+ bool initialized;
} davinci_clocksource;

static struct davinci_clockevent *
@@ -94,8 +95,9 @@ static void davinci_tim12_shutdown(void __iomem *base)
* halves. In this case TIM34 runs in periodic mode and we must
* not modify it.
*/
- tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC <<
- DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;
+ if (likely(davinci_clocksource.initialized))
+ tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC <<
+ DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;

writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR);
}
@@ -107,8 +109,9 @@ static void davinci_tim12_set_oneshot(void __iomem *base)
tcr = DAVINCI_TIMER_ENAMODE_ONESHOT <<
DAVINCI_TIMER_ENAMODE_SHIFT_TIM12;
/* Same as above. */
- tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC <<
- DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;
+ if (likely(davinci_clocksource.initialized))
+ tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC <<
+ DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;

writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR);
}
@@ -206,6 +209,8 @@ static void davinci_clocksource_init_tim34(void __iomem *base)
writel_relaxed(0x0, base + DAVINCI_TIMER_REG_TIM34);
writel_relaxed(UINT_MAX, base + DAVINCI_TIMER_REG_PRD34);
writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR);
+
+ davinci_clocksource.initialized = true;
}

/*
--
2.23.0
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